The 520's aren't bad speakers. I own them. But they're small and need to be used in the context that they were intended.
Make sure you're room is up to snuff -- ie you've addressed it's shortcomings (adding room treatments like absorption/diffusion, perhaps corner traps). This is true regardless of any equipment upgrade. Room is critical.
The other piece is matching the right amplification to the speaker. I don't know the specs on the Cambridge, but I know Ushers like good quality power, the more the better. You may be surprised if you add a more powerful amp to your speakers what they will sound like, and could give you the body you're looking for. If you still pursue speakers, try to determine that the Cambridge is a good match for them. You've already got a decent sub.
If you go with something like Aperion or Swan on your list (assuming buying new, Swan from The Audio Insider) or if you buy from someone like Audio Advisor, you get a return policy.
Make sure you're room is up to snuff -- ie you've addressed it's shortcomings (adding room treatments like absorption/diffusion, perhaps corner traps). This is true regardless of any equipment upgrade. Room is critical.
The other piece is matching the right amplification to the speaker. I don't know the specs on the Cambridge, but I know Ushers like good quality power, the more the better. You may be surprised if you add a more powerful amp to your speakers what they will sound like, and could give you the body you're looking for. If you still pursue speakers, try to determine that the Cambridge is a good match for them. You've already got a decent sub.
If you go with something like Aperion or Swan on your list (assuming buying new, Swan from The Audio Insider) or if you buy from someone like Audio Advisor, you get a return policy.